ode45  expects a function   f(t,y)  which takes two arguments and for
which the second argument is a vector.  Also, the output
must be a column vector.  Thus the following works:

f=inline('[v(2); v(3); -v(3)-v(2)-v(1)]','t','v')

In this case the call to ode45 looks like
[t,y]=ode45(f, ....

However, I think it is just as easy to write an m-file:

function dy=myf(t,y);
dy=zeros(3,1);  % makes it a column
dy(1)=y(2);
dy(2)=y(3);
dy(3)=-y(3)-y(2)-y(1);

Here, the call to ode45 looks like
[t,y]=ode45(@myf, ....

Note the use of the "@" symbol to create a function handle.  The inline 
form doesn't need it.